Visual investigation takes place at the museum. It follows preset protocols and standards, involving mavroscopy, technical photography and microscopy. Analytical investigation is mainly the province of our external partners in the CPN.
Until April 2012, the visual examination work space was located in a sculpture gallery. This was an asset in communicating the project to visitors, but eventually became a drawback. We ran out of space, and creating darkened conditions for technical photography was awkward. The work space therefore moved behind the scenes, but the communication function of the earlier space has been retained.
When a sculpture enters the work space, its history and any earlier conservation treatment has been researched. Its present state of conservation is described and the piece is systematically photographed in natural (Tungsten) light, followed by technical imaging to reveal traces of polychromy: Ultra Violet Fluorescence (UVF), Infra Red Reflectography (IRR) and Visible-Induced (infrared) Luminescence (VIL). The photographic documentation and investigation is followed by microscopy. Traces of pigment found may then be identified by non-invasive methods, primarily X-Ray Fluorescence spectrometry (XRF).
At this point, we may decide to turn to invasive methods. This involves removing pigment samples, usually the size of a full stop in a text. Such samples are subjected to analyses which may be destructive, involving the loss of the sample, or non-destructive.
The CPN external partners contribute staff time for a range of instrumental, analytical technologies for elemental pigment and colourant identification and characterization. The analyses carried out so far have included the use of the following: Scanning Electron Microscopy / Energy-Dispersive X-Ray spectroscopy (SEM/EDX) and Scanning Electron Microscopy / X-Ray Diffraction (SEM / XRD); Fourier Transform Infrared Spectroscopy (FTIR); Gas Chromatography – Mass Spectrometry (GC-MS; for binding media analysis); Raman Laser Spectroscopy; X-ray Fluorescence Spectroscopy (XRF; including portable XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS, for isotopic analysis).
The contribution made by the external partners to the project is absolutely vital and has so far, in principle, been provided free of charge. The present financial crisis makes it uncertain whether this can continue. In budget planning, payment for these services should now be foreseen.
These methods and their application in the project are the subject of a number of published articles.